Field
The disclosed and claimed concept relates generally to circuit interrupters and, more particularly, to a heater apparatus for use in a thermal trip of a circuit interrupter.
Related Art
Circuit interrupters are known for use in many applications. Circuit interrupters such as circuit breakers and other devices are typically employed to protect a portion of a circuit during certain predefined overcurrent conditions, under-voltage conditions, and other conditions.
Such circuit interrupters typically include one or more trip devices such as a magnetic trip, a thermal trip, etc., each of which is typically connected with an operating mechanism that is configured to move the circuit interrupter between an ON condition and a TRIPPED or an OFF condition when one or more of the predetermined conditions in the protected circuit are met. A magnetic trip typically involves some type of an armature which moves rapidly in response to magnetic fields that are developed within the circuit interrupter in the presence of a rapid current increase. A thermal trip typically includes a bimetal strip which deflects as a result of I2R heating of the bimetal strip in response to sustained current flow through the circuit interrupter.
While such trip devices have been generally effective for their intended purposes, they have not been without limitation. For example, in relatively low current applications, such as 20 Amperes or less, the I2R heat in the bimetal strip may typically be insufficient to provide a sufficiently prompt response to a sustained overcurrent condition. The thermal trip in such an application may be supplemented by a heater which is in the form of an electrical conductor that is electrically and thermally connected with the bimetal strip and which generates some additional I2R heat as a result of current flow through the circuit interrupter. Such additional I2R heat is thermally conducted to the bimetal strip in order to supplement its own I2R heat and thus enhances the deflection of the bimetal strip at a given current level. However, the addition of such a heater to the thermal trip within the interior of a circuit interrupter adds thermal, magnetic, and mechanical complexity to the circuit interrupter, and it thus would be desirable to provide a solution that meets certain shortcomings known in the relevant art.